This is the first time I am going to Hajj and I have already performed Umrah. Is it permissible to do Hajj al-Tamattu' (i.e. it involves performing Umrah and then Hajj, with one ihram for each) and intending to do Umrah on behalf of my mother? أحج لأول مرة وأنوي العمرة لأمي فما الحكم؟

All praise is due to Allah alone, and may the Salah and Salam of Allah be upon our Prophet Muhammad, his family and his companions. To answer your question, we say while seeking all the success from Allah: Hajj al-Tamattu' is to enter the state of ihram to do Umrah during the months of Hajj and then after completing the rituals of Umrah, beginning the rites of Hajj on the day of Tarwiyah (i.e. the eighth day of Dhul-Hijja). Thus, the Umrah you intend to do on behalf of your mother is considered part of the acts of Hajj al-Tamattu'. Your brother, Khalid al-Mosleh   24/11/2014